This invention relates in general to means for reducing the belt tension in a safety belt applied by the retractor rewind spring when the belt is in use. More specifically, the present invention relates to counterbiasing means for biasing the retractor reel in a belt unwinding direction when connected thereto and means for releasably connecting the counterbiasing means to the reel when desired to produce a belt tension reduced condition.
Various means have been provided in safety belt retractors heretofore for relieving or reducing the belt tensioning effect of the rewind spring on the belt when the belt is placed in use. It is common practice in the automotive industry presently to utilize safety belt retractors which employ retractor locking means sensitive to a change in vehicle inertia and/or an acceleration of the safety belt webbing off of the retractor of an amount in excess of a predetermined amount. In these types of emergency locking retractors, the seat belt is normally free to move inwardly and outwardly of the retractor, under the bias of the rewind spring of the retractor, during normal movements of the vehicle occupant about which the safety belt is placed when in use. The normal rewind springs employed generally have an increasing tensioning affect as the belt is protracted to a position of use increasing the possibly objectionable affect of the belt tensioning upon the occupant wearing a safety harness or a seat belt including such safety belt.
Exemplary of prior means for reducing the tension on a safety belt is that in U.S. Pat. No. 3,834,646 (Heath). In the Heath patent, the belt tension relieving means holds the retractor reel against rewind when the tension relieving means is activated until the safety belt is protracted further. In addition, the belt must be initially protracted, then retracted and then protracted once again to place the tension relieving means in operation. While this produces an effective tension relieving means, it has been found to be desirable to have a tension reducing means, as opposed to the relieving means of the Heath patent, and which is activated on a simpler belt manipulation.
An improvement in safety belt tension reducing means is disclosed in the co-pending U.S. patent application Ser. No. 627,875 filed Oct. 31, 1975 (Ulrich) which provides for a limited low tension travel of the webbing while in a low tension condition and which includes means for automatic setting and deactivating of the tension relieving means in response to normal manipulation of the safety belt to place it in use. In the exemplary embodiment of that application, however, the limited low tension travel for the seat belt is provided for by tension arm means pivotally mounted to the retractor and extending partially outwardly of the retractor frame for lateral engagement and movement of the safety belt webbing during the low tension travel provided therefor. This approach for a tension relieving means, while effective, introduces various complexities into the construction of the retractor, and its housing, which tend to increase the costs of manufacture thereof as well as integration into a vehicle safety belt harness installation.